There are known soft tissue biopsy instruments and devices designed as syringes comprising an outer cylindrical body having a piston slidably engaged therein, so as to define a suction chamber. A biopsy cannula extends from one end of the cylindrical body, and a stylet connected to the piston is movable within the biopsy cannula. Such a design is described in European Patent 0 173 653 to Zambelli, and is based on the Menghini needle.
When the stylet point projects from the cannula, it can be inserted through the skin into internal tissue, and suction is then developed by retracting the piston, pulling the stylet into the cannula. By a quick forward motion, the cannula cuts into the tissue, and a tissue fragment is retained therein by the vacuum. When the cannula is removed from under the skin, the vacuum is released by reinserting the piston in the cylinder, and the tissue fragment is dislodged and made available for lab analysis.
A problem with this and other existing biopsy devices is that the vacuum created by the piston is not sufficiently strong to insure retention of the tissue fragment. Thus, as the device is removed from the skin, there is a tendency for a portion of the tissue fragment to remain in place, and the amount of tissue available for testing is thereby reduced. These devices require the use of both hands for their operation.
Another method for biopsy procedures is described in U.S. Pat. No. 3,477,423, and features a product sold under the tradename "Tru-Cut", which is commercially available from Travenol Laboratories. In this design the stylet has a depression formed in its distal end, and this depression becomes filled with tissue when the stylet penetrates it. The cannula is slid over the stylet, cutting the tissue portion lodged in the depression, so that a larger quantity of tissue is then available for tests.
A drawback to the "Tru-Cut" design is that it is difficult to use with a very thin needle (gauge higher than 20), since the stylet is thin and not sufficiently rigid to penetrate the tissue, so it may bend or break, with risk of patient injury.
In addition, fine needle aspiration procedures are difficult, owing to the density of tissue which cannot easily be drawn into the small cannula diameter.
Existing tissue biopsy devices are of the single-use, disposable type, and rely on simple designs to achieve low manufacturing costs. As a design criteria, this tends to limit the use of mechanisms which can simplify the procedure.
Therefore, it would be desirable to provide a soft tissue biopsy device which can be adapted for use with high gauge needles, for obtaining required biopsy tissue quantities.
It would also be desirable to provide an easy-to-use tissue biopsy device capable of single-handed operation.